Are aluminum sprocket nuts legal in all classes?

[Bill Klindworth]

Are aluminum sprocket nuts legal in all classes?

[Allan Campbell]

No. lol

[Jim Dugger]

Bill,

Do these nuts simply hold a carrier together (with the drive force on other parts of the hardware) or are they subject to shear forces?

Most sprocket designs subject the bolts to shear forces, and I must warn you to NOT use aluminum fasteners in this capacity.

A quality aluminum (T6 grade) will only deliver about Grade-2 hardware hardness and durability. This is a safety issue, plain and simple. Sprocket nuts are typically grade 8 or higher, although you can use Grade 5 titanium and stainless hardware on them safely as well. If you elect to use SS or Ti, be sure to inspect for stretching on a regular basis.

Honestly, exotic fastener materials in these locations can be a PITA. Save your aluminum fasteners for bodywork and non-critical applications.

[Bill Klindworth]

There are the nuts that hold the sprocket on the carrier. The bolts remain steel
There is no mention in the rule book about them so I thought I'd ask (asking for a friend)
Seems like years ago it was in the rule book but perhaps my memory is not what it used to be :(
Perhaps it was the section about mods for superstock / supersport classes that says (paraphrased) if the mod is not mentioned it can not be done ?

Personally the few grams saved by use of aluminum nuts is not significant when I'm caring 10 extra pounds in my belly !

[Jim Dugger]

Sorry, I was confusing nuts for bolts.

Personally, I wouldn't do it. You are going to have to back way down on the clamping torque to use the Al nuts.

[Linz Leard]

As en engineer, let me state that aluminum as a sprocket nut is a excellent example of terrible engineering. Or the complete lack of engineering, actually. I'm not even a fan of aluminum fasteners with steel threads in an area where strength is the primary focus. I can list all kinds of reasons why aluminum sprocket nuts are bad idea: aluminum in any grade or temper is weaker than steel by a large margin and stretches easily, galls easily, is subject to stress, corrosion and cracking when any appreciable amount of torque is applied to it and over repeated usage cycles, age hardens fairly rapidly, and is subject to galvanic reaction when mated to steel studs. I could go on and on, but why?

Steel and Ti are all I'd ever recommend, and I'd recommend steel over Ti all day long.

I believe the race director and I are in agreement that aluminum sprocket nuts are not legal for any class due to structural integrity issues.

[David Branyon]

I'm with Linz, Jim, and Bill. Some things are illegal, some things are just not smart, and some things are both. This should fall in the 3rd category.

[Walter Walker]

The Race Director agrees.

[Bill Klindworth]

Thank you Linz & Walter